4000 DPI scanning example
This is a simple 4000 DPI scan example I put together to show my
friends how much detail I could pull out of film with my scanner. (And yes, I
know now that I oversharpened the images).
I used a Nikon LS-4000 to scan Provia 100 or Velvia (I can't remember which)
at 4000 DPI.
The photo of Delicate Arch was taken in 2001 in Arches National Park, Utah, using
a Nikon N90s with a Nikon 85mm F1.8 AF (non-D) lens on a tripod.
The pictures below give some idea of the level of detail possible from scanning a
35mm slide at 4000 dpi. The first image shows the entire scene as shot. Each
picture below was cropped and enlarged from the one scan.

Here is the entire scene. Can you tell there are at least 12 people in this shot?

Here is the upper left 1/4 of the shot. Now you can see the
people climbing around the arch area more clearly. I can see two people sitting
off on the left side, and one standing on a rock on the right, plus what looks
like about 5 more in front of or under the arch.

Cropped in even more tightly around the arch. Now you can make out someone
just to the left of the arch.

Cropped in tightly around the arch. I see three people standing under the arch,
three more just to the right, one (probably) mostly covered by the right side of
the arch, and one on a rock to the right.
Amazing amount of detail in film, and 4000 dpi scanning is not overkill. However,
storing 4000 dpi images is a bear. Scanning at 16
bits per channel at 4000 dpi and saving in TIFF format results in 100MB
files...